The present invention relates to foundations for towers in general and, in particular, to a foundation for telecom towers and similar applications.
In the implementation of a telecom network, a power transmission network or a similar network, first, sites are selected and planned, then building permits for the sites, including the tower sites, are obtained, and afterwards, the sites are built. In the conventional case, a concrete foundation is cast at the tower site. A normally prefabricated steel tower is assembled, erected and affixed to the foundation, in any of a number of known fashions, generally including screwing or bolting the tower base to the foundation. This provides a permanent tower facility, but takes a relatively long time to deploy, due to the fact that the foundation concrete must cure sufficiently to withstand the tower base loads before the tower can be erected and affixed to it.
Increasingly, new Telecom Networks (primarily mobile telephone networks) tend to be built under fast roll-out constraints. On the other hand, it is increasingly hard to obtain building permits for the sites (primarily the tower sites) of such networks.
Accordingly, there is a long felt need for, and it would be very desirable to have, a rapidly deployable telecom or similar tower, which would utilize a prefabricated foundation solution.
According to the present invention, there is provided a foundation for a tower, the foundation comprising a plurality of prefabricated slabs coupled together so as to function as a monolithic foundation.
According to one embodiment of the present invention the shape of the surface area of the foundation can be substantially square, rectangular, circular, octagonal or any other geometrical shape.
According to another embodiment of the present invention the foundation includes a plurality of layers, each layer including a plurality of adjacent slabs joined transversely to adjacent layers, wherein the thickness of each slab in a layer is substantially the same.
According to one embodiment of the invention the surface area of each slab is one half of the surface area of each said layer.
According to a preferred embodiment of the invention, each slab includes a plurality of horizontally spaced throughgoing substantially vertical bores for accepting long bolts or elongated connecting members having threaded at least end portions. Said bores further include lining sleeves.
According to yet another preferred embodiment of the invention, at least each slab at the bottom layer of said foundation, further comprises substantially vertical recesses at one end of said throughgoing vertical bores, wherein said recesses have a cross-section which is larger than the cross-section of said bores.
Further according to a preferred embodiment of the invention, the recesses have a specially shaped non-circular cross-section for housing said long bolts or connecting members, securing nuts, locking nuts, plate washers and non-rotating nut holding devices for preventing rotation of said connecting members when tightening said securing nuts.
According to a preferred embodiment, said recesses are arranged for snug fit housing of said heads of long bolts and securing nuts.
According to yet another preferred embodiment, said recesses further house non-rotating nut holding devices which have a non-circular cross section equal to or larger than the cross section of said securing and locking nuts, and are adapted to snug fit into said recesses and snug hold said locking nut, for preventing rotation of said connecting members. Said non-rotating nut holding devices comprise a substantially flat surface having surface area dimensions and contour suitable for snug fitting into said recesses, a circular hole suitable for inserting said connecting member and co-axial thereto, and two parallel walls projecting from said flat surface substantially perpendicularly thereto, wherein each wall is positioned at an equal distance from the center of said circular hole and spaced apart at a distance substantially equal to the length between two opposite ribs of said locking nuts for snug fit housing and holding of said locking nut. According to another preferred embodiment, said bottom layer slab further comprises a metal plate including holes co-axial with said recesses and bores, for distributing loads created by tensioning of said long bolts or connecting members and providing a support surface against which said heads of long bolts or securing nuts abut when said connecting members are tightened.
According to yet another preferred embodiment, all of said long bolts or connecting members or at least some of them, protrude from the top layer of the foundation for joining together all said layers of the foundation and connecting said tower to said long bolts or connecting members. According to still another preferred embodiment, each said layer includes slabs substantially similar to said bottom layer slab. According to one embodiment, the top layer includes slabs substantially similar to said bottom layer slabs turned upside down.
There is also provided in accordance with the present invention a method of preparing a foundation for a tower, the method comprising:
preparing prefabricated slabs including throughgoing substantially vertical bores for receiving elongated connecting members;
preparing a site having a desired area;
placing a first layer of said prefabricated slabs on the site;
placing a second layer of said prefabricated slabs transversely on said first layer, while;
aligning said throughgoing receiving bores; and
joining together said first and second layers by means of said elongated connecting members passing through said aligned throughgoing receiving bores.
There is further provided in accordance with the present invention a method of preparing a foundation for a tower, further comprising placing additional layers of prefabricated slabs on said second layer and joining together all the layers by means of elongated connecting members passing through said aligned throughgoing bores in all the slabs.
The method according to another preferred embodiment of the present invention, further comprises placing prefabricated slabs having substantially vertical recesses at one end of said throughgoing vertical bores, at the bottom layer. According to a preferred embodiment, the method further comprises placing slabs substantially similar to said bottom layer slabs at any of the layers.
The method according to yet another preferred embodiment, further comprises placing slabs substantially similar to bottom layer slabs turned upside down at the top layer.
According to another preferred embodiment, said method further comprises the step of assembling onto bottom end portions of connecting members said securing nuts, said non-rotating nut holding devices and said locking nuts before inserting connecting members through said first layer, extending upwardly.
According to yet another preferred embodiment of the present invention, said method further comprises the step of inserting connecting members through said first layer, extending upwardly, before the step of placing the slabs of the first layer on the ground.